<!DOCTYPE html>
<html>

<head>
    <meta charset="utf-8">
    <title>菜鸟教程(runoob.com)</title>
    <style>
        div {
            width: 100px;
            height: 100px;
            background: red;
            position: relative;
            animation: myfirst 5s linear 2s infinite alternate;
            /* Firefox: */
            -moz-animation: myfirst 5s linear 2s infinite alternate;
            /* Safari and Chrome: */
            -webkit-animation: myfirst 5s linear 2s infinite alternate;
            /* Opera: */
            -o-animation: myfirst 5s linear 2s infinite alternate;
        }

        @keyframes myfirst {
            0% {
                background: red;
                left: 0px;
                top: 0px;
            }

            25% {
                background: yellow;
                left: 200px;
                top: 0px;
            }

            50% {
                background: blue;
                left: 200px;
                top: 200px;
            }

            75% {
                background: green;
                left: 0px;
                top: 200px;
            }

            100% {
                background: red;
                left: 0px;
                top: 0px;
            }
        }

        /* Firefox */
        @-moz-keyframes myfirst {
            0% {
                background: red;
                left: 0px;
                top: 0px;
            }

            25% {
                background: yellow;
                left: 200px;
                top: 0px;
            }

            50% {
                background: blue;
                left: 200px;
                top: 200px;
            }

            75% {
                background: green;
                left: 0px;
                top: 200px;
            }

            100% {
                background: red;
                left: 0px;
                top: 0px;
            }
        }

        /* Safari and Chrome */
        @-webkit-keyframes myfirst {
            0% {
                background: red;
                left: 0px;
                top: 0px;
            }

            25% {
                background: yellow;
                left: 200px;
                top: 0px;
            }

            50% {
                background: blue;
                left: 200px;
                top: 200px;
            }

            75% {
                background: green;
                left: 0px;
                top: 200px;
            }

            100% {
                background: red;
                left: 0px;
                top: 0px;
            }
        }

        /* Opera */
        @-o-keyframes myfirst {
            0% {
                background: red;
                left: 0px;
                top: 0px;
            }

            25% {
                background: yellow;
                left: 200px;
                top: 0px;
            }

            50% {
                background: blue;
                left: 200px;
                top: 200px;
            }

            75% {
                background: green;
                left: 0px;
                top: 200px;
            }

            100% {
                background: red;
                left: 0px;
                top: 0px;
            }
        }
    </style>
</head>

<body>

    <p><b>注意:</b> 该实例在 Internet Explorer 9 及更早 IE 版本是无效的。</p>

    <div></div>

</body>

</html>